Process and apparatus for clarifying coal slurry and the like



Jan. 26, 1937. F. VOHMANN ET AL PROCESS AND APPARATUS FOR CLARIFYINGCOAL SLURRY AND THE LIKE Filed Nov. 50, 1934 Patented Jan. 26, 1937UNITED STAES PATENT OFFICE PROCESS AND APPARATUS FOR CLARIFY- ING COALSLURRY AND THE LIKE ritory Application November 30, 1934, Serial No.755,446 In Germany January 5, 1933 6 Claims.

The invention relates to a process and apparatus for clarifying coalslurry and the like by causing the solid constituents of the slurry tobe separated under the action of a precipitating agent while the slurryis flowing downwardly, whereupon the clarified liquid is permitted torise gently in a settling receptacle and to flow away, the solidconstituents being collected in the receptacle.

According to the invention the slurry is subjected to the action of aprecipitating agent adapted to induce turbulence, such as potato flouror similar flake-forming additions and the solid constituents areseparated from the downwardly flowing slurry in inclined hollow bodies,the discharge ends of which extend into a receptacle much larger incross-section where the liquid that has been clarified rises immediatelyafter leaving the hollow bodies and flows away at the top, while thesolid constituents, unaffected by the rising liquid, sink to the bottomof the receptacle and become concentrated adjacent a discharge opening,whereupon they are drawn off from the receptacle at intervals orcontinuously with the concentration desired and dried in slurrycentrifuges or on suction filters.

The hollow bodies are relatively small in crosssection. They are notidentical with the inclined settling surfaces which are provided inclarifying vessels of known construction, in order to effect locallimitation of unsuitable movements such as will hinder the process ofclarification, or in order to assist in causing the solid constituentsthat sink in the rising slurry to be precipitated in the clarifyingreceptacle.

It has been found as the result of many laboratory experiments that itis essential to clarify the slurry not whilst it is rising but as it isflowing down, because in this case the speed at which the solidconstituents settle is increased by the speed at which the slurry isflowing. In clarifying apparatus in which clarified water and slurrymove in opposite directions the settling speed is reduced even ifsettling is not completely arrested.

It is important that the clarifying process v should be completelyfinished in the hollow bodies efore the slurry reaches the receptacle inwhich the liquid rises, in order that the solid constituents that havebeen removed shall not be exposed to any upward fiow, but can settlequietly on the bottom of the receptacle where they accumulate andconcentrate until they are drawn off continuously or at intervals whenrequired.

A fundamental condition for obtaining the rapid and perfectclarification of the slurry is the particular form, as to length andshape, of the hollow bodies, the cross-section of which must be muchsmaller than that of the receptacle in which the liquid rises and intothe lower part of which the hollow bodies extend and in which the speedof rising is so small that eddies do not form.

Furthermore, it is advantageous to provide a number of hollow bodiessimilar to one another and of such dimensions, and so disposed, that allare charged to exactly the same level. The hollow bodies may be insideor outside the receptacle in which the liquid rises and may be of alength suificient to enable the clarifying process to be carried outcompletely. In order to save space and to assist the clarifying process,it is advisable to form the hollow bodies as helices arranged around orin the receptacle in which the liquid rises, the inlet ends extendinguniformly into a feed channel which is fed by a supply pipe by way of adistributor hood with inclined feed surface.

According to the invention, the inlet ends of the hollow bodies may beprovided with slots, notches, holes or the like, in order to ensure theuniform entry and passage of the slurry into the hollow bodies, evenwhen the inflow is intermittent. The slots are advantageously of suchconstruction that their cross-section increases in the upward direction,whereby any differences in height of the inlet ends are corrected, andtheir inlet cross-section is automatically adjusted to the quantity ofslurry entering at any moment. The inlet ends may however, be providedwith nozzles fitted by means of a screw-thread or the like in order thatthe height at which they are placed may be adjusted.

Several constructions of apparatus according to the invention arediagrammatically illustrated by way of example in the accompanyingdrawing.

Fig. 1 is a central vertical section through a clarifying apparatus inwhich the receptacle is of cylindrical form and the separating bodiesare grouped in conical form;

Fig. 2 is a section on the line 22 of Fig. 1;

Fig. 3 is a vertical section through a clarifying apparatus in which thereceptacle is of rectangular form;

Fig. 4 is a top plan view of Fig. 3;

Fig. 5 is a side elevation, partly in section illustrating a clarifyingapparatus in which the separating bodies are of spiral form and externalto the receptacle, and,

Fig. 6 is a partial top plan view of Fig. 5.

of the distributor h'ood m into the delivery chan- Figures 1 and 2illustrate a receptacle 0; circular in cross-section, in which theinclined hollow bodies I) converge like rays downwardly towards thecentre of the receptacle. The hollow bodies b may be in the formof'helices in order to obtain the necessary length and inclination. Inthis case they lie advantageously close against the inner or outer wallof the receptacle. The inlet ends d, which all extend regularly intoinlet channel 0, are fed from a delivery device e above the inclinedsurface of the conical distributor hood while the discharge outlet forthe clarified liquid is provided beneath the inlet channel 0.

Figures 3 and 4 show inverticalsection and plan respectively arectangular clarifying receptacle a into which extend in rows a numberof hollow bodies 17 connectedat th'eir upper ends-to receivers or inletchannels for the slurrydisposed along the opposed sides of thereceptacle, their outlet ends h being so disposed that the solidconstituents separated out in the hollow bodies can travel downwardly onthelower inclined walls g-of the receptacle, whereas the water rises byreason of its lower specific gravity. The inlet channels are indicatedat c. The shape of the -outletendsh illustrated in these-figures, thatis to sa-y, the provisiono't an upward flare by which the cross-sectionis increased, has the further purposeofenabling the'liquid that'has-been-c1ari Tied to riseeven before leaving the hollow bodies.

Figures v5 and 6 illustrate a construction par- 'ticularly suitable forcarrying out the clarifying operation, which construction is seen :inFigure 5,

on the left, in section, and, on the right, in elevation, and in Figure6 from above.

This clarifying apparatus comprises the recep- "tacle a and a number ofhollow'bodies b which are wound-in the form of'helices around thereceptacle, andwhose upper -ends, all projecting the 'samedistance'abovethe bottom of the feed-channel-7c, are formed at 'i with slots whichof acrosssect'ion that increases towards the upper end of the slot. They arefed with slurry-continuously or at intervals abovethe -distributor hoodm through the inlet conduit -Z,' the slurry having first beenthoroughlymixed, by means of an agitator with a precipitati-ng :agentwhich -may consist of part of the slurry' that has already settled. IThe slurry flows over "the inclined surface 01.

nel and at this point rises like arising water level horizontallyuntilit is able'to'pass through the slots in the hollow'feed bodies.dInsteadzofxslots,

notches, holes, nozzles orgthe like may be .provided at the upper endsof the .bodies b.

Laboratory experiments have rshown that...in the hollow bodies turbulentstreams are produced under the-action of theprecipitatingagent, theeffect of which is toseparate ither solid constituents from thedownwardlyimoving slurry and ".to cause them to travel along thelowerwall of the hollow bodies. The speed of precipitation isv increased bythe slurry which is flowing in the same direction.

The lower ends'o of the hollow bodies extend into the lower part of thereceptacle 11 At .this point the'clarified water, indicatedat w, at oncecommences to rise in the receptacle a and then issues forththrough thedischarge tubefpwhich communicates with the interior .of' thereceptacle, whilethesolid constituents sink. onto the inclined wall qofthe receptacle and pass to the drawingoff position 1" Without beingaffected-in any way by .the upward. fiowof the liquid. On "the way alongthe wall of the receptacle at the upper than in any-other knownclarifying apparatus in 10 which the solid constituents are separatedout from'the rising slurry.

The clarifying operation produces very good results giving a largeoutput and occupying lit- "tle space. "The fine particles may berecovered almost completely from the slurry and the clarified liquid maybe used again.

Weclaim:

1. A process for the uninterrupted clarification of coal slurry and thelike involving the "use of :a precipitating agent, consistinginsupplying the slurry treated with the precipitating agent :at the headof a receptacle of suitable farm, inducing the downward flow of the saidslurry and precipitating agent in a pluralitypof streams of smallcross-sectionto the lower part of the receptacle where the streams uniteto form a body of liquidof a larger cross-sectional area than thecombined cross-sectional area of the streams, said streams beingdelivered into the body-of liquid so as to .be confined to;a limitedpart of the said areaso that theseparated solid constituents are therebyconcentrated collecting and further concentrating in the lower partofthereceptacle the solid constituentssepasrate-cl. out in thedownwardfiow of the slurry-and causing the clarified liquid of.theslurry torise upwardly in the receptacle, and withdrawing it at thetop of the receptacle, the concentrated lsolidlconstituents beingwithdrawn'from the receptacle.v

2. Apparatus for' the clarification of coal slurry and ;the .like,comprising a receptacle, opposite- ..ly disposed channel-like supplymembers positioned uponthe opposite walls of the receptacle to the saidsupply members and extending aat .opposite angles to the side of thereceptacle to the -lower part thereof, and outlets'from the receptaclefor the solid constituents and .for the clarified liquid, the lower partof the receptacle having inclined walls upon which the solidconstituents may collect.

3. Apparatus for the clarification of coallslurry and the likecomprising a receptacle, a supply member for the slurry supported at thehead of the receptacle, a number of tubular bodies symmetricallyarranged and extending from the head of the receptacle-at an inclinationto the horizontal. and opening at the lower end into the lower part .ofthe receptacle, the said hollow bodies serving to effect the clarifyingoperation, and outlets from the receptacle for the solid constituentsand for the clarified liquid.

.4. Apparatus for the clarification of coalslurry and the like,comprising a receptacle, achannellike supply member for the slurryextending end thereof, a number of tubular bodies connected at the upperend of the receptacle to the supply member at a uniform elevation andextending from the upper end of the receptacle in,

symmetrical disposition and at an inclination to the horizontal to thelower part of the receptacle and opening freely therein, and outletsfrom the receptacle for the solid constituents and for the clarifiedliquid respectively provided in the lower and upper parts of thereceptacle.

5. Apparatus for the clarification of coal slurry and the like,comprising a receptacle, a channel-like supply member for the slurryextending along the wall of the receptacle at the upper end, a number oftubular bodies connected at the upper end of the receptacle to thesupply member and extending in symmetrical disposition at an inclinationto the horizontal to the lower part of the receptacle and opening freelytherein, means provided at the upper ends of the tubular bodies forefiecting the uniform charging of the said bodies with slurry from thesupply member and outlets from the receptacle for the solid constituentsand for the clarified liquid.

6. Apparatus for the clarification of coal slurry and the like,comprising a receptacle, a channel-like supply member for the slurryextending along the wall of the receptacle at the upper end, a number oftubular bodies connected at the upper end of the receptacle to thesupply member at a uniform elevation and extending in symmetricaldisposition at an inclination to the horizontal and helically inrelation to the walls of the receptacle to the lower part of thereceptacle and opening freely therein, the said hollow bodies serving toeffect the clarification of the treated substance, and outlets from thereceptacle for the solid constituents and for the clarified liquidrespectively provided in the lower and upper parts of the receptacle.

FRITZ VOHMAN'N. ERICH TRiiMPELMANN.

